Manager Brad Ausmus said Zimmermann's four-inning simulation revealed some improvement from his rough outing Saturday -- in which he lasted just one inning plus four batters. But the team is waiting to see how the 30-year-old feels Thursday before determining his next step.
"I thought he looked better, more consistent mechanically, coming right at the hitter with his delivery. He definitely looked better," Ausmus said.
Ausmus, who spent 18 years as an MLB catcher, said that when Zimmermann's mechanics were "right" he had more life on his fastball and greater depth to his breaking balls. Ausmus did not, however, sound as if he is banking on Zimmermann making his next start. Instead, the manager indicated there is further work to be done before Zimmermann returns to the rotation.
"I think it's just a matter of getting consistent with the mechanics, that's all," Ausmus said.
Zimmermann inked a five-year, $110 million deal as a free agent last winter. He had a sensational first half of the season – in April alone, he posted a 5-0 record with a 0.55 ERA -- but his second half has been scuttled by injuries.
The native of Auburndale, Wisconsin, spent two stints on the disabled list -- each one lasting a month or more -- for a right neck strain that has presented challenges in both diagnosis and recovery. Zimmermann was shelled in each of his return performances after being activated off the disabled list.
On Aug. 4, he was given the hook after surrendering six runs in 1.2 innings pitched. Saturday's start against the Orioles was eerily similar. Zimmermann was replaced in the second inning after giving up six runs in one-plus innings pitched. He faced a total of 10 batters.
Zimmermann said he will consult with the team's managerial and medical staff before deciding the next course of action.
"We'll see," Zimmermann said. "Taking it one day at a time, and today was a good day."
The Tigers are also dealing with an uncertain return date for injured third baseman Nick Castellanos, who has been sidelined since the first week of August with a broken bone in his hand.
Castellanos took one at-bat against Zimmermann in Wednesday's simulated game but did not make a second appearance at the plate. The 24-year-old infielder was still experiencing some discomfort swinging the bat against live pitching.
Castellanos was unsure what that means for his timeline -- originally slated to be four to six weeks.
"I don’t have that luxury of going to rehab, so we’re going to try to do everything in-house. How long that takes, it’s all going to depend on how my hand feels," he said. "I don’t really have a crystal ball. If I wake up tomorrow and my hand feels great, maybe I’ll have a chance to hit back on the field before the day game tomorrow, and start scheduling some more simulated games in Cleveland."
Ausmus wasn't expecting Castellanos to feel 100 percent and pain-free when facing Zimmermann on Wednesday.
"I wasn't surprised, to be honest with you. It was still bothering him in soft toss and [batting practice] so it didn't shock me that he felt [it] with the velocity," Ausmus said.
Asked if the Tigers are concerned that Castellanos may not be able to come back and contribute before the end of the regular season, Ausmus said: "We're getting closer for sure, but there's no reason for not progressing until we run out of time, I guess."